Water pipe used as electrical ground?

My electrical panel looks like it's connected to a copper water supply for ground.

If the copper pipe is unioned to a galvanized pipe that goes to the main, is the electrical ground still intact - or is there a dialectric that breaks the ground?

If there is a break, is there a normal procedure to re-establish ground?



p.s. I guess I'll get out my meter to test connectivity.


{Moderators note: I moved this down here to the electrical section from the plumbing section. We will get our professional electrical advice here soon.}

get out meter to test connectivity

Be VERY aware, this is NOT your "ground" in the way that you probably think it is!

True, the water pipe may be used as a grounding electrode if certain conditions are met (jumping the wire around the union with two clamps is one of them), and it certainly is your water bond, BUT...this is NOT where you get your "safety ground" that causes a breaker to trip when something hot hits a metal box for instance.
THIS "ground" is created by the neutral to ground bond in the main service panel/disconnect.

Speedey......I was wondering if he was saying that the panel was using the connection to the water pipe as the ONLY ground. I have heard of that happening, and I assume it is not proper??

jimbo said:

Speedey......I was wondering if he was saying that the panel was using the connection to the water pipe as the ONLY ground. I have heard of that happening, and I assume it is not proper??

Click to expand...

No, the earth will probably never trip a breaker.


Here is a very good article to read http://ecmweb.com/grounding/electric_shocking_truth_grounding/

The earth will almost never be the "only ground".
Pretty much every residential service in this country will have a bonded neutral. THIS is your ground at the third prong of a receptacle and the green wire at a fixture.
The water pipe is only a grounding electrode, just like a ground rod, and also serves as the water piping bond. A grounding electrode has it's purpose, but it is NOT to "create" a ground as is commonly assumed.
A water bond is just to prevent the piping systems in the house from remaining live with voltage if they come in contact with a live wire.

Regarding grounding electrodes, I think every electrician should have this printed out, and every electrical related web site should have this as a sticky post:

250.4(A)
(1) Electrical System Grounding Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

Chris75 said:

Here is a very good article to read http://ecmweb.com/grounding/electric_shocking_truth_grounding/

Click to expand...

This is a great article. I've had it bookmarked since it came out.

Some dielectric "nipples" have a plastic inner ring but a metal outer pipe. The inner plastic prevents electric current from flowing on the inside of the pipe (where the water is and where it counts), but the outside metal conducts electricity and thus continues the ground.

I don't know about other dielectric unions.

You can test with a continuity tester, but an accurate test would only be with the coupling disconnected from the pipes.

If in doubt, you can install two water pipe ground clamps on either side of the union and use a large gauge copper wire jumper to connect the two.

Other sources of a broken ground are at some water meters which can use rubber grommets or at a water heater which may electrically isolate the hot water piping from the cold water piping. So good to place ground jumpers in these locations as well.

If you have plastic water pipe - "Forget about it!"

In addition to a cold water pipe ground, it is best to also have two ground rods placed 6 ft. apart and connected to the main service panel via a separate ground wire. Check local code for size of ground rods and ground wire sizes.

P.S. Turn off the main power before installing any ground jumpers or messing with any ground wiring. 99% chance there will not be a problem by leaving the electricity on, but that 1% zap can get you!

grounding

When I asked the electrical inspector about using a dielectric union on the house main between copper galvanized, especially since a dielectric is cosmetic and not functional, he said they had to install a jumper across the union. When I asked him if that didn't pretty much negate the dielectric union, he had no answer, just said to do it.

hj said:

When I asked him if that didn't pretty much negate the dielectric union,

Click to expand...

How so? The two dissimilar metals are still not touching.
He's right though. Anything that breaks the continuity of the water piping system MUST be jumpered.

electrolysis

Electrolysis does not require that the metals touch. The current flow is through the water, exactly like with a water heater anode rod. Dissimilar metals just screwed together do not deteriorate until you add water as an electrolyte.